Ignition control



ov 3G, 3943. D. B. WARING IGNITION CONTROL 3 Sheets-Sheet 2 Filed June 25, 1945 1B .A a

UWM M Nom 30, 1948. v D. B.-WR|NG 2,455,344

IGNITION CONTROL Filed June 25, 1945 3 Sheets-Sheet 3 Patented Nov. 30, 1948 S TET OFFHCE EGNITION CNTROL Dana B. Waring, East Hartford, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application June 25, 1945, Serial No. 601,437

pensating an automatic engine ignition timing,

system for changes in combustion characteristics resulting from the operation of engine'controls or regulating devices such as a Supercharger speed setting mechanism or a water injection apparatus.

A further object is to provide improvements in control devices for internal combustion aircraft engines.

Other objects and advantages will be apparent ,from the specication and claims, and from the accompanying drawings which illustrate what is now considered to be a preferred embodiment of the invention.

In the drawings, Fig. 1 is a schematic view showing an ignition timing apparatus incorporating a compensator, or control device, constructed and arranged according to the teaching of this invention.

Fig. 2 is an enlarged sectional view of the compensator or control device of Fig. 1.

Fig. 3 is a sectional view along the line 3-3 of Fig. 2.

Fig 4 is a sectional view of a water injection regulator and shows how the compensator of Figs. l, 2 and 3 may be operatively connected with a wat-er injection apparatus.

8 Claims. (Cl. 123-117) Fig. 5 is a partial sectional view of the supercharger speed selector valve and the change speed supercharger drive gear unit diagrammatically shown in Fig. 1, and including the connection for the compensator of Figs. 1,. 2 and 3.

Fig. 6 is a sectional View of the selector valve in the high gear ratio position.

Changes in the combustion characteristics of the charging fluid of an lengine require corresponding changes in spark advance, or the time at which ignition occurs with respect to piston position, for optimum engine performance. According to this invention, the ignition timing of an engine may be automatically compensated for changes in charge combustion characteristics, and particularly for those resulting from a change in the operating characteristics of a supercharger for the engine, or from the introduction of a comltered fuel chamber 62.

bustion modifying ingredient, such as water, into the engine charge.

Referring to the drawings, Fig. 1 shows one form of the present invention as applied to an ignition timing apparatus of the type disclosed in the Jarvis application referred to above, and to which reference is made for a detailed description of the basic ignition system illustrated in the drawings of this application.

An engine, such as a radial aircooled aircraft engine, is supplied with charging fluid by a main stage supercharger having an impeller I2 mounted -in a blower case, a portion of which is shown at l0. The impeller is driven by the engine crankshaft (not shown) through a tailshaft 36', a change speed gear transmission 38' and a quill shaft 28'. Transmission 38 may' be controlled by a selector valve |80, in a manner similar to that described in Hobbs Patent No. 2,323.601, granted July 6, 1943, and as illustrated i-n Figs. 5 and 6.

Intake air ows to the impeller l 2 in an amount regulated by throttle 24 through a manifold 22, which may be fed directly from the ambient air or from the outlet of an auxiliary supercharger stage, in a known manner. The rate of ow by weight of air passing to the engine is measured by the carburetor air metering section comprising the venturis 30, 30', impact tubes 36, and altitude compensator 32. The rate of flow by weight of fuel to the engine is regulated by fuel valve 52, supplied with fuel by pump 46. The valve is actuated by an air head diaphragm 28 in the air metering section and the fuel head diaphragm 64 of the fuel metering section. As fully described in the said Jarvis application, or in Palmer application Serial No. 529,104, filed April 1, 1944, assigned to applicants assignee, the air and fuel head diaphragms cooperate to maintain a fuel pressure drop or metering differential, which is a function of the rate of flow by weight of engine intake air, across metering section or control body 58, between unmetered fuel chamber 54 and me- Thus the ow of fuel is regulated in predetermined ratio to the ow of intake air. This ratio may be manually set for rich or lean mixtures by the head 11 on the valve 18, which controls ow through jet 6B. In the idling power range, idle valve I5I may be used to control the mixture strength. Economizer valve opens jet 'l2 partially or fully to enrich the mixture in the high power range.

Metered fuel flowing from the control body 58 through line 68 may be raised in pressure and directly injected into the engine combustion charnbers in a known manner, for instance as disclosed in Beardsley application Serial No. 302,749, led November 3, 1939, assigned to applicants assignee, now Patent No; 2,447,265 issued August 17, 1948, or it may be injected into the intake air by the discharge valve |45 and fuel spinner |54 as shown in Fig. l, in the manner fully described in the Palmer application referred to above.

The engine spark plugs are supplied with ignition current by magnetos i4, i6 driven by the engine through a gear train includingmagneto drive gears |08, H8 and the bevel gears |04, |88. mounted on adjustable cages interconnected by link |32. Link |32 is moved to the right or left by piston |24 of the servo motor 0|, to advance or retard the ignition timing. kSpring 38 biases the piston to the spark retard position.

Servomotor |85 is connected with a fluid pressure source |52 and drains |54, |56 by lines |68, |68. The application of pressure from source |52 to one or the other side of piston |24 is controlled by a valve plunger |62, in the operating unit |86. The valve plunger is actuated by diaphragm i12 subjected by lines |18, |16 to the pressure rise directly across the supercharger. When the pressure rise increases to a predetermined value diaphragm |12 is forced downwardly to compress spring |18 and move plunger E62 in position te connect source |52 with line |58 and to connect line |60 with drain |56, and thereby move piston 24 to the right to advance the spark. When the pressure rise is below a predetermined value, spring |18 will hold plunger |62 and piston i243 in the spark retarded position. If desired, stops may be provided, as shown at |88 and |65, to limit the movement of the plunger |82.

Spring |18 is so selected as to hold the operating unit |44 in the retard position when the engine is idling. When the engine power output is increased to the cruising range, the increased pressure rise created by impeller I2 is sufficient to overcome the force of spring |18 and advance the spark. The pressure rise across the supercharger varies approximately with variations in engine power and has been found satisfactory not only as an actuating pressure for the spark advance operating unit but also as a control or datum pressure which regulates or determines the point at which the timing is advanced as engine power output enters the cruising range.

As the engine power output is increased beyond the cruising range and enters the high power range, it is desirable to retard the ignition timing to prevent detonation and for other reasons. This is accomplished by the spark advance control unit |80, best shown in Fig. 2, comprising a by-pass valve |90 for bleeding fluid from line |14 to line |16 by way of lines |84, |92. Because the iiow capacity of valve |90 is materially greater than the flow capacity of restrictions |98, 200 in supercharger rim and throat lines |14, |16, the pressures on opposite sides of diaphragm |12 will be approximately equalized when the valve |80 is open, thus placing the operating unit |44 in the retarded spark position regardless of the value of the superoharger pressure rise.

Valve |90 is held closed by a spring 201 and is opened by a diaphragm 86 subjected by lines 2||, 2|0 to the fuel metering pressure differential between chambers 54, 62. This pressure differential is an accurate measure of intake airflow (and therefore engine power) and consequently diaphragm |86 may be arranged to compress diaphragm spring 209 and valve spring 201 to open valve |80 at a predetermined point 0X1 the engine power output curve, which point is pre!- erably at the extreme upper end of the cruising power range and which may be selected by spring 288 and spring 201.

The diaphragm spring urges diaphragm |86 against a stop flange |81 and bottoms on a piston 380 reciprocably mounted in a cylinder 302 in the control unit |80. The piston is moved in one direction (until it abuts shoulder 304) by a pressure responsive device such as a fluid tight expansible chamber or rubber inner tube 308 and is urged in the other direction (into abutment with shoulder 306) by the spring 209.

Fluid under pressure from conduit 3|0 is admittedto the expansible tube 308 through a uid tight connection comprising pipe 3| I, nipples 3 2, Sie and plug 3|5. When pressure fluid is so admitted, tube 308 expands and forces piston 800 to the left, to compress spring 209 and increase the datum force or preload on the spring and thus increase to a higher predetermined value the amount of the fuel metering head across diaphragm |86 which is required to open by-pass valve |88. When the supply of pressure fluid to line 8|@ is terminated, fluid drains from tube 388 through pipe 3H', now restriction 3|8 and the drain tube 320, relieving the pressure in passage Biil, 3|| and enabling the tube to collapse 4and unload the spring 2 89 by permitting piston 388 to be moved into abutment with stop 305. The now capacity of restriction 3|8 is preferably made very small, so that an application of fluid pressure to line 3| 0 is sufficient to expand tube 388 even though a small amount of the fluid drains through the restriction. Drain tube 320 may, of course, be arranged to return the uid draining therethrough to the tank or sump (not shown) from which the line 3|0 is supplied.

Tube 308 is positioned within a recess 322 and the tube and the piston 300 surround the extension 324 of the valve seat 326. The valve seat and its extension are xed within the casing and the extension has a bore therein for guiding stern 328 of valve |90 in its reciprocal movements. The extension has a cap 330 xed thereto, for guiding the movements of the cup shaped diaphragm washer 332. The cap may also serve as an inner piston stop cooperating with the outer piston stop 304. Diaphragm |86 is also guided by the rod 334. Seals (not shown) are preferably provided where the rod 334 passes through casing |80 and where stem 328 passes through extension V324, but it is not necessary to seal off the chamber 322 from the diaphragm metered fuel chamber. Therefore piston 300 need not be fluid tight.

Fluid line 3|() is diagrammatically shown in Fig. 1 as connected to the selector valve |80, which governs the gear ratio of the supercharger drive 38. This valve, shown in detail in Figs. 5 and 6, includes a handle 208 which is manually moved between the low gear ratio position of Fig. 5 and the high gear ratio position of Fig. 6. to control the speed ratio of the transmission 38.

Transmission 38' (Fig. 5) includes a lay or clutch shaft 250 to which the pinion 248 and the clutch elements 268, 210 are splined and on which the gear members 252 and 254 are rotatably supported. Gear 252 has a clutch face or friction band 254 thereon with which the clutch element 268 may be engaged, by axial movement o f the element along the splines on the shaft 250, to form a relatively low speed ratio drive for the impeller I2. Gear 254 is provided with a similar band 266 which is engaged by axial movement of element 210 to form a high speed 'ratio drive.

Power is transmitted from the engine crankshaft to the impeller |`2 through the tail shaft 36', the gear 246 (which incorporates a spring drive unit 245). pinion 248, shaft 250 and either low speed gear 252 or high speed gearf254, depending upon which of the clutch elements 268, 21C) is engaged.

Each clutch is urged toward disengaged position by a spring 212 which biases the clutch elements 268, 210 away from the clutch bands 264, 266. To engage one or the other of the clutches fluid under pressure (such as engine lubricating oil) is admitted to one or the other of the cylinders or chambers 214, 216, respectively associated with each clutch. The parts are so arranged that fluid admitted to either chamber acts on the corresponding clutch element to move it axially, like a piston, to compress the `spring 212 and to engage the clutch element with the surrounding gear.

Admission of fluid to the chambers 214, 216 is controlled by valve |80, shown in the low speed ratio position in Fig. 5, with the low gear clutch 268, 252 engaged. When the valve handle 208 and shaft 206 are in the position shown in this figure, fluid is admitted from the pressure source 2|8 to the pipe 2|5. From there it passes through the inner bore 94 to the low clutch member 214, Where it forces element 268 into driving contact with band 264 and engages the transmission in low gear ratio, to drive the impeller at a low speed relative to engine speed. When pressure fluid is being admitted to pipe 2|5 the high ratio clutch chamber 216 is connected to the drain 200, by

bore |30 and pipe 2|3. Consequently spring 212 will hold the high clutch element 210 disengaged when the low clutch element 268 is engaged.

Rotation of shaft 206 by handle 208 from the low ratio position of Fig. 5 to the high ratio position of Fig. 6 connects the pressure source 2|6 to the high clutch line 2|3 and connects the low clutch line 2|5 to the drain 200. Thus, in'the high ratio positionof valve |80 pressure fluid is admitted to chamber 216 to engage the transmission in high gear ratio and the low clutch chamber 214 is connected to drain, permitting spring 212 to disengage the low clutch.

When the valve |80 is in the low speed ratio position, and the supercharger is being driven at a relatively low speed relative to the engine, the low clutch lines 94 and 2|5, and consequently the line 3| 0 connected thereto, contain fluid under pressure. In the high speed ratio, position of valve |80 the lines 94 and 2|5, and consequently line 3|0, are connected to drain 200, and there will be little or no pressure therein. Therefore the tube 308 of the spark advance control unit will be expanded so as to hold piston 300 against stops 304, 330 when the supercharger is being driven in low gear ratio; and the tube will be collapsed, with piston 300 abutting stop 306, when the supercharger is being -driven in the high gear ratio.

Thus the tube 308 will be expanded and the control unit 80 will be actuated to open valve |90 at a predetermined higher value of intake airflow to equalize the pressures in lines |14, |16 and retard the spark when the supercharger is in low gear ratio; and the tube 308 will be collapsed and the control unit actuated to retard the ignition timing at a predetermined lower value of intake airflow when the supercharger is in high gear ratio.

ferential overcomes the force of springs 209, 201).

But with the apparatus shown in Figs. 1-3, 5 and 6, the point at which the spark is retarded as the power increases to the high power range will be varied in accordance with changes in supercharging conditions. In high blower ratio, the spark will be moved to retard position by the opening of valve |90 at a relatively low engine cruising power, thus tending to prevent detonation such as might otherwise occur with advanced spark and high power in high blower ratio. In low blower ratio, valve |90 will remainclosed and the spark will be maintained in advance position until a relatively high engine cruising power is reached, thus enabling the full benefit of advanced spark to be obtained in the relatively high cruising power range when the blower is in low ratio andv detonation is not so likely to occur.

The tube 308 may also be connected with other sources of fluid pressure which vary with engine operating conditions, so as to reset the datum of the control-unit in accordance with other changes in operating conditions resulting in changes in the combustion characteristics of the engine charge.

Fig. 4 shows such an alternative source of uid pressure for the fluid pressure responsive device 308. In this ligure, a coolant or anti-detonant such as Water is admitted to the water regulator |06 through line I2, fed by a pump from a Water supply tank (not shown). As specilcally described in the Palmer application No, 529,104,

valve |22 in regulator |06 is actuated by a dia- A phragm |26 between chamber |24, subjected to unmetered fuel pressure by line |28, and the unmetered water chamber |30.

When it is desired to introduce water into the engine intake air the electrical solenoid |02 is energized, either manually or automatically, causing valve |05 to lift and admit water under pressure from line ||2 to chamber 6. The resultant increase in water pressure in chamber ||6 opens check valve ||8 against the force of spring y| i9 and the water flows into chamber |20. From there it flows into chamber |30 in an amount regulated by valve 22, which is actuated by diaphragm |26 so as to maintain the Water pressure in chamber |30 equal to the unmetered fuel pressure in chamber |24. As water discharge line |36 is preferably connected to the fuel discharge line 68, the pressure drop across the Water metering jet |34 will be maintained equal to the fuel metering pressure differential and the water will be introduced into the engine charge in predetermined ratio by weight to engine intake airflow.

According to the modicatio'n of Fig. 4, the line 3|0 from the control,unit is connected to thechamber ||6 of the water regulator, instead of to the supercharger selector valve as shown in Figs. 1-3, 5 and 6. With such an arrangement, when valve |05 is opened and Water begins io flow to the engine the pressure in line 3|0 will increase along with the rise in pressure in chamber ||6. This causes tube 308 to expand and reset the control unit |80 so as to open valve |90 only when the engine intake airflow and power output has increased to a higher value than would be required to open the valve when water isgnot being injected. If water injection is terminated, for instance by closing valve |05, the pressure in line 3i0 will drop (the restriction 3I8 may be provided for this purpose) and the tube 308 will collapse and unload spring 209 and thereby reset the control unit to open at a lower intake airiiow.

With the arrangement of Figs. 1-3, 5 and 6 the control unit is compensated in the manner described above to regulate the ignition timing in accordance with changes in supercharging conditions, and speciiically for changes in the speed ratio of the supercharger drive. I

In the modification of Fig. 4, the control unit is compensated in a similar manner to regulate the ignition timing in accordance with changes in the condition of the engine charge, and speciflcally for changes in the composition of the engine charge.

It is to be understood that the invention is not limited to the speciiic embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claimz/ 1. In an engine ignition timing mechanism, a iirst source of iiuid pressure, a second source of iiuid pressure, meansresponsive to fluid pressure from said iirst source for advancing the ignltion timing, means responsive to uid pressure from said second source for retarding said timing, and fluid pressure responsive means independent of said fluid pressures from said first and second sources for controlling said timing in a:cordance with variations in an engine operating condition.

2. In an aircraft engine having a supercharger and a multi-speed ratio transmission for driving said supercharger by said engine, mechanism lncluding an adjustable intake airow responsive device for varying the ignition timing of said engine in accordance wtih variations in engine power output, and means for adjusting said device in accordance with changes in the speed ratio of said transmission.

in accordance with changes in the speed of said supercharger relative to the speed of said engine.

5. yAn ignition timing system for an engine having a supercharger, comprising, an operating unit actuated by the pressure rise directly across said supercharger for advancing the ignition timing, an adjustable control unit connected to said operating unit and actuated by a pressure differential which is a measure of engine intake airflow for retarding the ignition timing, and

means indicative of changes in the combustion characteristics of the engine charge for adjusting said control unit.

6. The system of claim 5, in which said operating unit is actuated to advance the timing at a predetermined value of said pressure rise and in which said control unit is actuated at values of said fluid pressure differential which are determined by said adjusting means.

7. An ignition timing system for an engine having an engine driven supercharger, comprising, an operating unit actuated by the pressure rise directly across sain. supercharger for advancing the ignition timing, an adjustable control unit connected to said operating unit and actuated by a pressure differential which is a measure of engine intake airflow for retarding the ignition timing, and means indicative of a change in the speed of said supercharger relative to the speed of said engine for adjusting said control unit.

8. An ignition timing system for an engine having a supercharger, comprising, anV operating 3. In an ignition timing apparatus for an engine having a supercharger, mechanism responactuated by a change in a i'iuid pressure which change is indicative of achange in the detonation characteristics of the engine charge for adjusting said control unit.

DANA B. WARING.

REFERENCES CITED The following references are of record in the lc of this patent:

UNITED STATES PATENTS Number Name Date 1,787,686 Kerr Jan. 6, 1931 2,064,864 Temple Dec. 22, 1936 2,217,364 Halford Oct. 8, 1940 2,320,886 Quiroz June l, 1943 2,383,898 Udale Aug. 28, 1945 2,414,322 Mock Jan. 14, 1947 

